Tungsten (W) is typically used in multiple applications for semiconductor device fabrication. For example, W has been used in the chemical vapor deposition (CVD) metal filling of features such as, for example, word lines in three dimensional (3D) NAND devices. Presently, bulk W is deposited in word lines in which an oxide layer has already been formed. However, the inventors have discovered that the bulk W fill may produce undesirable effects. For example, W fill induces bowing in the substrate. Other issues with W CVD are seams formed when W fills a word line, high resistivity, the use of fluorine (F) which causes damage to the oxide layer, and damage caused to the substrate from the necessary etching step required to remove deposited W from the sidewalls of the word line.
Therefore, the inventors have provided embodiments of an improved method and apparatus for depositing cobalt in features formed in a substrate.